The present invention relates to a composition for ceramic dielectrics which is very fine in grain size and has a prolonged life and further obtains a capacitance value which improves a temperature dependence of capacitance.
Conventionally, as a high dielectric constant composition for ceramic dielectrics, there has been used a barium titanate of which the Curie point is made to be shifted to about a room temperature by adding strontium titanate, barium stannate, calcium stannate, or barium zirconate as a shifter. However, the grain size of the thus treated barium titanate is not less than 5 .mu.m, consequently it is unsuitable for a raw material of such a product as a layer-built capacitor which is used in high electric field. Namely, in the case where the grain size is large, an electric field strength falling on one grain becomes higher and consequently a breakdown voltage becomes lower and defects due to voids concentrating at the grain boundary also are made to be increased, and a life becomes shorter, thus resulting in a lowering of reliability.
The present inventors have investigated to overcome the above mentioned defects of conventional compositions and provide a composition for ceramic dielectrics which is very fine in grain size, not more than 5 .mu.m, and has a prolonged life and have found out that a composition for ceramic dielectrics obtained by adding oxides of Ce, Zr and Ca to the barium titanate, instead of the above mentioned shifter, is refined to be very fine in grain size. Thus, the inventors have accomplished the present invention.